More on Wooden Propellers

Scan of wood propeller torque information from Sensenich.

Wooden Propellers

Let me start by saying there's no prettier wood than what's on a wooden aircraft propeller (in my opinion that is). Some of the most beautiful wood work you'll see is, in fact, on my engine test clubs. I have a gorgeous 4 blade propeller and also a walnut test club for a Cessna 150 that will knock your eyes out. 

That said, it brings me to a problem I found at the shop a few weeks ago. A few people around know about the new American Champion 7EC that's up at a farm about ten miles from here. The owner bought the airplane brand new in the fall of 2007 and the airplane now has a total of 75 hours on it. I've done all the work on it so far, which on a brand new plane and 75 hours, doesn't amount to a whole lot. The plane is parked under a open shed hangar on the farm and is pretty much protected from the elements except for what sun light can get to it. There's the problem. I noticed a few months ago that the finish on the prop was beginning to fade. It was no longer that beautiful, glossy look but rather a dull flat finish. The owner tried to wax it, but to no avail. Here, you can get an idea of what it looked like when it was new :

Now a few months ago, it still pretty much looked like this only more dull and milky looking. I saw the airplane again about 3 weeks ago and here's what it looks like now:

  
Notice how the finish is literally gone from the trailing edge of the blade and you can now see raw wood showing. Notice the raw "hair" of the wood now totally exposed to the elements. I've never seen wood weather that fast. 

Notice also that the finish is not flaking or peeling, but just gone as if it evaporated off the surface. The wood is also beginning to turn a gray shade which is not good either. I have since shipped the propeller back to the manufacturer (Sensenich), whom is the only repair station authorized to perform the refinish on this particular propeller. They said that this is UV damage and is caused solely by contact with the sun. They assured me that they could take care of this and it would look good as new. 

So the point of all this is if you ever have the opportunity to own an airplane, airboat, test club, or whatever propeller that's made out of wood, be sure if it is even exposed to sunlight that you have a cover over it. Keeping it clean and covered, it should last for years. 

Right now, I'm just glad my airplane has a metal prop on it. ;-)
 

Beech F33A Electrical System Repairs

The F33 has been plagued lately with a problem of the low voltage light coming on accompanied with an ear-piercing squeal through the speaker/headphones. The only way to stop it was to turn the alternator off, then back on again. The ammeter didn't work, but the pilot thought there was no problem with that because he had a JPI. What he didn't know was that the JPI shows buss voltage only and not amp load. The only way to tell if the alternator system was working was to see if the buss voltage dropped. So, after further investigation, here is what I found. I don't believe that you could burn this shunt worse if you used a torch. 

 So when I replaced the shunt, I noticed the terminal block and the fuse holder looked like it had been down 40 miles of bad road, so I opted to replace these at the same time. Used new wiring and terminals since the originals looked like crap. So here it is all wired up and ready to go. Got it in and everything seems fine now. No squeal, ammeter works as advertised, etc. All in all it came out pretty good ! 

 

Some Pix of my latest project

Replacing old standard nav lights with L.E.D. units and comet flash strobes.